1. Field of the Invention
The present invention relates to a duplexer module in which a duplexer used for isolating a reception signal and a transmission signal from each other is provided on a multilayer substrate or a printed substrate.
2. Description of the Related Art
Duplexers are adopted for front-end portions of cellular phones and the like. In some cases, a multiband-type front-end portion compatible with a plurality of communication systems whose frequency bands are different from one another is configured using a plurality of duplexers (for example, refer to Japanese Unexamined Patent Application Publication No. 2007-124202).
The above-mentioned front-end portion includes a duplexer, a power amplifier, and a directional coupler, which are compatible with each of an 800 MHz band and a 1.9 GHz band. The duplexer isolates a transmission signal and a reception signal, which correspond to a band, from each other. The power amplifier amplifies the transmission signal using electric power supplied from a power-supply line. The directional coupler transmits a portion of the electrical power of the transmission signal to a monitoring line so as to monitor the transmission signal. In such a front-end portion, when interference occurs between signals in individual bands, there is a risk that communication quality is lowered. Therefore, the shapes of internal ground electrodes are set so as to prevent interference between individual bands from occurring.
While it is possible to reduce the interference of signals between individual bands on the basis of the configuration of the above-mentioned front-end portion, it is difficult to fully prevent the interference of signals between the transmission signal and the reception signal in a same band from occurring. In particular, with the development of the downsizing of duplexer modules in recent years, when a power amplifier and a directional coupler are included, problems have occurred in that the transmission signal and the reception signal interfere with each other due to signal leakage from the monitoring line or the power-supply line and receiving sensitivity is deteriorated, or the like.
Usually, while signal leakage occurring between lines in the duplexer has been considered in line design for signal lines through which a transmission signal, a reception signal, and an antenna common signal are transmitted, the signal leakage has not been fully considered in the layout design of mounting electrodes, owing to requests from assembly manufacturers intending to facilitate wiring lines for duplexer modules.